This invention relates to wireless local area networks, which may use protocols such as IEEE standard 802.11 or the Bluetooth protocol. In such wireless local area networks bubble units communicate with a local area network or a computer through fixed devices called access points. In some systems, such as systems available from Symbol Technologies, assignee of this application, a cell controller is provided which is interconnected to RF ports, which together function as access points in an 802.11 system.
In conventional wireless local area networks, using either access points or RF ports, there is a need to supply the access points or RF port as the fixed wireless communication devices with both electrical power and data network connection to enable the access points or RF ports to couple communications between a mobile unit and a fixed computer. For purposes of this specification the term access points will be used to include RF ports operating with a cell controller.
In conventional technology providing a facility, such as a university or industrial facility, with a wireless local area network, requires that separate cables be provided to each access point supplying electrical power on one cable and data network communications on a second cable. In some instances, wherein RF ports are used as access points, power may be supplied over ethernet cabling that provides both electrical power at low voltage and data network communications to an RF port using a single set of cables. Even in this situation, the routing of cables throughout a facility to be serviced can be one of the largest costs of installing a wireless local area network. In addition, if such cables are installed over existing construction, they can be unsightly and ruin the appearance, for example, in a hospital or office environment. One approach to eliminate the requirement of providing data communications cables throughout a facility is to provide data networking connection by means of wireless repeaters and/or networks. Using this approach the access points do not have a wired network connection, but communicate among themselves to a single access point that is connected into the network. Packets move from the wired network via a single access point or a plurality of access points to other wireless access points through wireless data communications. The access points organize themselves to optimize packet routing while avoiding packet loops.
In some instances communications between access points can be provided using a first radio and communications for which mobile units may be provided using a second radio.
The choice of using one or two radios in the wireless access point depends on the capacity requirement. If a single radio is used, its airtime must be divided between receiving messages from other access points and relaying those messages to the mobile units being served by the access point. Despite a potential reduction in capacity of a wireless network, in many applications large amounts of data traffic are not experienced and a single radio device can be used. A still existing problem with wireless local area networks that are interconnected by wireless data communications is that the distributed access points still require electrical power. Routing of electrical power to suitable locations for access points can involve considerable expenditure.
It is possible to design access points that plug into existing electrical outlets in a facility, but traditionally the location of such electrical outlets, usually low on walls, is inconvenient for the desired location of access points, which is on the ceiling of a facility.
There is an object of the present invention to provide access points which can be installed onto existing lighting fixtures in a facility and provide complete freedom from wiring in connection with the installation of a wireless local area network.